Spark plug



`luly 15, 1924.

. c. F. KETTERING SPARK PLUG Filed Jan. 11

kllll Patented July 15, 1924.

UNITED STATES PATENT OFFICE.

CHARLES F. KETTERING, Ol' DAYTON, OHIO, ASSIGNOB TO THE DAYTONENGINEmING LABORATORIES COIPANY, A (lOllolltA'lloNrl 0F OHIO.

SPARK PLUG.

Application led January 11, 1918. Serial No. 211,425.

ING, a citizen of the United States of' America, residing at Dayton,county of 6 Montgomery, and State of Ohio, have invented certain new andusefulImprovements in Spark Plugs, of which the following is a fullclear, and exact description.

This invention relates to spark plugs and has for its object theprovision of means for-cooling certain portions thereof which aresubjected to a high degree of heat.

Further objects and advantages of the presentinvention will be apparentfrom the following description, reference being had to the accompanying`drawings, wherein preferred embodiments of the present invention areclearly showns In the drawin Fig. 1 is a longltudinal sectional view ofa spark plug embodying the present inventlon; and

Fig. 2 is a bottom plan view thereof.

Referring to the drawing, 20 designates the shell having a lowerthreaded portion 21, adapting the shell to be attached to the enginecylinder. Within the shell and adjacent its lower end are mounted shellpoints 22. The shell is threaded internally at 23 and has an annularrecess 24 for a purpose to be described. 25 designates the center'electrode having a tube portion 26 extending down into the shell andterminatin in a head portion 27 at its lower end. Said head portion 27carries a center point 28, a portion of which is located adjacent theshell points. The tube 26 is threaded externally at its upper end at 29.A sleeve of insulating material 30 Surrounds the tube andl extends fromthe head 27 to apoint slightly below the threaded lportion 29.Surrounding the sleeve 30 andv superimposed in the order named are theinsulating spacer 31, the lower packing gland 32 having a flange 33seating in the recess 24, the upper packinggland 34 having a flange 35,and a bushing 36 of porcelain or other insulating material. A clampingnut 37 ,y centrally boredy to receive the packing glands 32 and 34, hasscrew-threaded engagement with the threaded portion 23 of the shell, andis provided at its upper end with an annular recess 38 for the receptionof the iange 35 of thel upper gland 34. A washer 39 surrounds the tu e26 and extends over the bushing 36. A radiator nut 40 having fins 41 iscentrally tapped for engagement with the threaded portion 29 of the tube26. A terminal nut 42 is centrally tapped for engagement with theaforesaid threaded portion 29.

The interior wall of the. tube 26 is provided with a coating of amalgam43 which may be applied by means of a method descrlbed in the co-pendingap lication of Thomas Midgley, Jr., Serial o. 211,224, filed Jan'. 10,1918. A small quantity of mercury 44 normally occupies a space at thebottom of the tube. A plug 45 welded, or otherwise, permanentlyconnected with the upper end of the tube, seals the chamber containingthe mercury. By tightening'up nuts 37 and 40, it will be seen thatglands 32 and 34, which are composed of a soft material, will be causedto ow and make a perfect seal between the sleeve 30, the nut 37 and theshell 20. f l The operation of this device is as folows:

When the center contact is heated by the burning gases in the cylinder,the heat therefrom passes into the head 27 and into the mercury 44 whichis caused to expand and to boil and evaporate. The vapor from theboiling mercury will transfer its heat in an effective manner to thewalls of the tube, and particularly the upper portion of the wallthrough the medium of the amalgam coating 43. From the vwall of the tubeheat-will pass to the radiator nut 40 and be dissipated therefrom intothe atmosphere by means of radiator fins 41.

The mercury vapor being cooled, on giving upits heat in the mannerdescribed, will condense and return to the bottom of the tube, again toreceive heat from the center contact and to transfer said heat in themgner described, to the upper end of the tu In small spark plu s of thesize used generally in automobile engine work, the diameter of thechamber in the center electhere is provided a vent member consisting ofseveral small wires twisted loosely togethei extending from the well ofmercury at the'bottom of the chamber to the upper-end thereof. lt hasbeen found that the mercury does not collect in the interstices betweenthewire strands of member 5t), and therefore the vapor underneath theclogging bod v of mercury has a fiee pasi `sage upwardly through member5t), whence said vapor may iind its way to a point above the mercury andcan force the same downwardly to the bottom of the chamber. Thisfeature, however, is not nl v invention but is described and claimed inthe. patent of Thomas l\lidgle v` Jr., No. 1,328,051, patented 1 Januarylith, 1920.

lt is apparent from the foregoing description that there has beenprovided a spark plug having a self-contained cooling system which isautomatic and thoroughly efficient and reliable in operation. Theconstruction of the spark plug is very simple and therefore conducive toeconomy in manufacture and easy disassembling for repair.

It has been discovered that the use of mercury as a cooling medium forspark plug electrodes is particularly advantageous for the followingreasons: Mercury has a high vaporization point and therefore will notdevelop such a high vaporization pressure as would be the case in waterwhen subjected to the temperature resulting from the heat of explosionwithin the gas engine cylinder.

Furthermore, this high vaporization point is, as has beendiscovered,-ju'st slightly below the spark plug temperature which ispresent in the operation of explosions of the present type; 4whereas thenormal vaporization of water is far below this temperature point.

1n addition to this, mercury has the further advantage in that it is achemical element instead of a compound, and therefore does not tend tobreak down into any constituent elements while operating as a coolingmedium for a spark plug electrode.

`While the form of mechanism herein shown and described constitutes apreferred form of embodiment of the invention, it is to be understoodthat other forms might be adopted, all coming Within the scope of theclaims which follow.

That is claimed is as follows:

1. In a spark plug, the combination with a plug shell; of an electrodeinsulated therefrom and having self-contained cooling provisionsincluding a chamberprovided With a chamber lining of metallic amalgam,and a quantity of fluid metal located Within said chamber.

Q. In a spark plug, the combination with a plug shell; of an electrodeinsulated therefrom and having self-contained cooling provisionsincluding a chamber provided with a chamber lining of metallic amalgam,and a quantity of mercury located within said chamber.

3. ln a spark plug, the combination with a plug shell; of an electrodeinsulated therefrom and having self-contained cooling provisionsincluding a chamber provided with a chamber lining of metallicamalgam',l a quantity of mercury located within said chamber, and aradiating member carried by the upper cud ot' the electrode.

4. In a spark plug, the combination with a shell carrying a contact; ofa center electrode mounted in the shell but insulated tlu-refroin. saidelectrode comprising a head portion and a tube portion which provides acentral chamber extending from the head portion. an amalgam lining forthe tube portion; a quantity of mercury in the tube p0rtion, and meansfor sealing the end of the tube; and a radiating member secured to thetube portion 'adjacent the end opposite the head portion.

5. In a spark plug, the combination with a shell carrying a contacthaving an annular recess and an interior screw-threaded portion; of acenter electrode consisting of a tube portion partially extending downinto the` shell and having a threaded upper end portion, and of a headof larger diameter than the tube, closing the lower end of the tube; acenter point mounted on the head portion; an insulating sleevesurrounding the tube portion and extending from the head to the threadedportion of the tube; an insulating spacer; a lower packing gland havinga flange seated in the annular recess in the shell; an upper packinggland having a flange; an insulating bushing, the spacer, glands andbushing being superimposed in the order named and surrounding theinsulating sleeve; a clampinglnut surrounding the glands and locatedbetween the flanges of the glands, and having an exterior screw-threadedportion engaging the screw-threaded portion of the shell, and having anannular recess to receive the flange of the upper gland; a Washersurrounding the tube portion and extending over the insulating bushing;a radiator nut, having heat radiating fins, en-

gaging the screw-threaded portion of thetube; a terminal nut'engagingsaid screwthreaded portion; an amalgam lining for the tube; aquantity of mercury in the tube; and a plug sealing the upper end of thetube.

6. 1n a spark plug, the combination with .a plug shell; of a centerelectrode supported' by said shell but insulated therefrom, said andarranged to contact with said head pore e ctrode including a hollow stemportion tion of the electrode. 10 1ndaiead potioi; a center plug plointem- In testimony whereof I aiix my signature.

e e in the ea portion' an cool ing pro- 5 visions contained within saidhollow stem CHARLES F' KETTERING' port-ion including a lining of mercuryamal- Witnesses: gam for the stem portion, and a quantity of J. W.MCDONALD,

mercury located within said stem portion IRVIN A. GREENWALD.

